Aircraft having rotative wings



March 17, 193]. DE LA |ERVA Re. 18,002

AIRCRAFT HAVING RCTATIVE WINGS Original Filed March 26. 1927 v x j B 134. 9 R 2 7,)? G D7 '6 -INl ENTOR.

Reiuued Mar. I7, 1931 UNITED STATES PATENT ol-rlca JUAN DI LA CIEBVA, OF MADBID, SPAIN, ASSIGNOB TO ZPITGAIBN ('JIERVA AUTOGIBO COMPANY OF AMERICA, A CORPORATION OF DELAWARE uncmr'r navmo aora'rrvn wmos Original No. 1,882,894, dated September 4, 1928, Serial No. 178,708, filed March 29, 1997, and in Great Britain April], 1928. Application for reissue filed Augult 16, 1930. Serial 110.475,?95.

This invention relates to aircraft having rotative wings and particularly to under-carriages or landing gear for aircraft of the type embodying a freely rotative h ngedwing system such as that described in my patent s ecification No. 1,590,497.

In or or to prevent damage to the articulated wing structure by sudden strong gusts of wind it is desirable that the angle of incidence of the wings in a machine of this character should be as nearly as possible zero when the aircraft is stationary on the ground. It is necessary on the other hand that the win should have a relatively reat positive 16 inci ence when taking off, an my present invention aims at providing anunder-carriage for aircraft-of this character such that the air-craft has two positions of rest, the one in which the incidence of the lifting sur- 90 faces is approximately zero to enable the machine to stand with little or no danger, and the other in which the incidence is sufliciently positive to enable the machine to take off. Primarily, according to the present inven- 25 tion, I provide an under-carriage, for aircraft of the character referred to, in which the landing elements proper, such as wheels or wheels and skidsare so disposed with relation to the center of gravity of the air-craft that the latter when at rest possesses two positions of equilibrium, one in which the longitudinal axis of the aircraft is substantiall horizontal and the angle of incidence of the wings approximately zero, and the other in which the tail-skid or other rearmost landing element is in contact with the ground or other surface and the angle of incidence of the wings is positive.

For this purpose the under-carriage may embody a pair or more of principal landing wheels so disposed that their axles lie in rear of the v ertical plane thru the center of gravity of the aircraft when the latter is resting with its longitudinal axis substantially horizontal, and in advance of said vertical plane when the tail-skid or other rearmost landing element is in contact with the ground, and a wheel or wheels in advance of the principal 60 wheel or wheels to support the aircraft in the first mentioned stationary equilibrium.

To enable the aircraft to be readily moved from one position of equilibrium to the other the displacement of the axles of the principal position of landing! wheels from the vertical plane throng the center of gravity of the aircraft may be relatively small so that the pilot by raisingor lowering theelevator or controllable tail plane, may cause the slip stream from the propeller or propellers to rock the aircraft from one of the said positions to the other.

To support the aircraft in its substantially. horizontal position of zero incidence either forwardly disposed landing wheels or skids may be em loyed. In an amphibian aircraft the principal wheels and the forward wheels or skids may be mounted in or upon the'floats in the case of seaplanes or the hull in the case of flying boats, and since the forward landing speed is small it may be unnecessary to provide means for withdrawing the wheels or skids into the floats or the hull, for landing u on water. i

A further eature of the resent invention consists in mounting theskids, or floats in the case of seaplanes, in such a manner that they are permitted a restricted pivotal movement about vertical axes, with suitable centralizing springs or other devices acting to maintain said skids or floats normally parallel to the fuselage but allowing them, when the aircraft lands with a lateral speed, to set themselves in the direction of the resultant speed. To accomplish this the vertical axes Fig. 2 is a similar view but showing the forward landing wheels replaced by skids.

Fig. 3 shows an application of the invention to a seaplane, and

Fig. 4 diagrammatically illustrates an arrangement in which the landing elements are capable of restricted pivotal movement about vertical axes as aforesaid.

In all of these figures A denotes the fuselage of the aircraft and i8 B the longitudinal axis, being the axis of thrust of the propeller 'C. Theint w re resents the center of gravity 0 the aircra and D denotes one of a pair or more of principal landing wheels secured to the fuselage through any convenient system of shock absorbers, diagrammatically indicated at D.

The line G G re resents the horizontal surface upon which t e aircraft rests in one position and Gr G the horizontal surface in the other position. The axles D of the wheels D are so. disposed with relation tothe center of gravity a: of the aircraft that the vertical plane, represented by' the line :2: y, through the center of gravity :0 is in advance of the axles D when the aircraft is in substantially horizontal position, which is therefore a position of equilibrium. In this position the angle of incidence of the wings E" is an substantially zero. Although only forwardly I and rearwardly extending wings of the rotative system are shown, it will be obvious that the incidence of laterally extending wings will be more nearly zero than when the aircraft is tilted back as hereafter mentioned.

In 1 a forwardly disposed wheel or wheels is or BIGPIOVldBd to maintain the substantially horizontal osition of the aircraft and in Fig. 2 a ski or skids H are employed for this purpose, the skids being used as aforesaid only in cases where the forward landing speed is relatively very small.

The other position of uilibrium of the aircraft is that represented y the contact of the principal wheels D and a tail skid J with the surface represented by the line G G, the aircraft having been rocked back about the axles D. In this position the vertical plane represented by t e line a: 3 through the center of gravity w is behind the axles D thereby v ensuring the state of equilibrium in this 081- by the action of the fstlig tion, in which the angle of incidence o the wings E is sufliciently positive to enable the aircraft to take off.

The displacement of the lines a: y and a: 3 from the wheel axlesD is preferably small, for instance such that thecoupll: produced stream m the progller C u n the li or depressed elevator is sufliclent to rock the aircraft from one positionsto the other.

I In Fi 3 the principal landing wheels D and ski Hare-mounted upon the floats L of a seaplane; the condition as to the relative positions of the axlesD and the center of gravity a: of the aircraft being the same as that above described.

Fig. 4 illustrates diagrammaticall a construction in which each skid H toget er with its landing wheel D is mounted to permit a restricted pivotal movement about a vertical axis M which is in advance of the center of friction of the said landing elements with the surface landed upon. The landing elements are in this manner enabled to set themselves parallel to the line of the resultant speed whenever the aircraft lands with a lateral as well as a forward speed. Elastic elements (not shown) of any suitable type, e. g. springs, are provided to maintain the skids normally arallel to the longitudinal axis of the aircraft or the direction of flight.

This construction may be similarly a to the form of constructionshown in ig. 1 where forward landing wheels are used.

What I claim is 1. An aircraft having sustaining means including aerofoil surfaces rotatably mounted for actuation by relative air-flow and having means permitting displacement thereof with respect to their mean rotative path, means for supporting the aircraft on the ground, and means whereby the general mean plane of rotation of the sustaining means may be set at different stable angles with respect to the ground with the craft at rest.

lied

2. An aircraft having sustaining means inv eluding aerofoil surfaces rotatably mounted for actuation by relative air-flow and having means permitting displacement thereof with respect to their mean rotative path, means for supporting the aircraft on the ground, and means whereby the general mean plane of rotation of the sustaining means may be set at different stable angles with respect to the ground with the craft at rest, said supporting means including in its structure sai mentioned means.

3. An aircraft including supportin blades mounted for rotation by relative airow and having means permitting displacement thereof with respect to their mean rotative path, means for supporting the craft at rest on theground with the general mean lane of rotation of the blades substantially 'orizontally disposed with respect to the ground and means for supporting the craft at rest on the ground with the general mean plane of rotation of the blades angularly disposed with respect to the ground.

4. An aircraft comprising a fuselage and propelling means, a supporting system com prising freely rotative win s articulated to the axis of rotation and a apted to be revolved by the relative air flow duri flight and an undercarriage comprising principal landing wheels having their axles disposed close to a transverse vertical plane assing through the center of gravit of the aircraft, advanced landing elements 'sposed in front lastof the principal landing wheels to support the aircraft 1n;stationary uilibrium with its longitudinal axis substantially horizontal and the angle of incidence of the wing system approximately zero and a rear landing element such as a tail-skid to support the aircraft in conjunction with the principal landing wheels in another stationary position of equilibrium in which the wing system has a 10 relatively great ositive angle of incidence.

5. An aircra t comprising a fuselage and propelling means; a supporting system comprising freely rotative win articulated to the axis of rotation and adapted to be revolved by the relative airflow during flight and an undercarriage including principal landing wheels, supplementary supporting means pivotally mounted in front of the rincipal landing wheels, said landing whee begoing so disposed that their axles lie in the rear of the verticalplane through the center of gravity of the aircraft when resting on the wheels and supplemental supporting means and the said wheels being in advance of said a :5 vertical plane when the tail-skid of the aircraft is in contact with the ground.

6. An aircraft having sustainin means including aerofoil surfaces rotatab y mounted for actuation by relative air-flow and having no means permitting displacement thereof wit respect to their mean rotative ath, means for supporting the aircraft on tl ie ground, and means whereby the general mean plane of r0- I tation of the sustaining means may be set as at different fore-and-aft angular positions of stability with respect to the ground with the craft at rest.

7. An aircraft including supporting blades mounted for rotation by relative air-flow 4 and having means permitting displacement thereof with respect to their mean rotative path, means for su porting the craft at rest on the ground wit the general mean lane of rotation of the blades substantially ori- 45 zontally disposed with respect to the ground and means for supporting the craft at rest on the ground with the general mean plane of rotation of the blades dis osed'at an upwardly and forwardly inc 'ned angle with 50 res ct to the ground. a. I

n testimony whereof I have hereunto signed my name.

' JUAN DE LA CIERVA. 

